Relay system



Aug; 4, 1936. y w. R. KOCH 2,050,059

RELAY SYSTEM Filed March 1, 1934 OJYIC 15 L 1:5: j jig: j! 7 4T we F933INVENTO/Ef Patented Aug. 4, 1936 UNITE-D STATES RELAY SYSTEM Winfield R.Koch, Camden, N. J., assigner to Radio Corporation of America, acorporation of Delaware Application March 1,

7 Claims.

My invention relates to thermionic or electric discharge tubeutilization networks analogous to the one shown on page 167 et seq.,volume 2, textbook on Wireless Telegraphy, (British) by Rupert Stanley,1923 edition.

More particularly, the invention relates to relay systems whereinthermionic or electricdischarge tubes are utilized-as triggeredcontrolling elements for operating current responsive and otherelectrical devices connected in circuit therewith. In aspeciflc form ofthe invention, a multi-vibrator type of circuit is employed for thepurpose of providing a-relay circuit having the characteristics of anamplifier and certain characteristics of a multi-vibrator.

Heretofore, the multi-vibrator, so called as exemplied by thepublication referred to, has been utilized principally for theproduction of oscillations rich in harmonics. Insofar as I am aware,

however, the multi-vibrator or an equivalent cir- 'affected by changesin atmospheric conditions.

It is, accordingly, an object of my invention to provide an amplifier ofthe direct-connected type that shall not require a high potential platesupply source, and coupling condensers between inter-connected anodesand grids While maintaining a high degree of stability.

Another object of my invention is to provide an amplifier or relay ofthe trigger-action type, the output current from which need notnecessarily be proportional in amplitude to the input potential appliedthereto. l

Another object of my invention'is to provide a relay of the typereferred to wherein the duration of the output current is independent ofth duration of the input potential.

Another object of my invention isl to provide, in a relay of the typereferred to immediately above, means whereby the said relayautomatically returns to normal condition upon removal of inputpotential.

Another object of my invention is to provide a trigger rel-ay of thetype referred to that shall have an voutput current which goes through adefinite cycle in response to a change in input 1934, Serial No. 713,621

(Cl. Z50-36) potential and automatically returns to normal value.

Another object of my invention is to provide a trigger relay that shallybe responsive only to input potentials having a predetermined duration.

Another object of my invention is to provide an oscillator of themulti-vibrator type, characterized by the fact that from the outputcircuits of the several tubes included therein wave-forms havingdiffering frequency characteristics may be l0 obtained.

A still further object of my invention is to provide an oscillator ofthe type referred to that shall be capable of oscillating more stronglythan oscillators of conventional multi-vibrator types, and l5 withgreater stability. p

The foregoing objects and other objects ancillary thereto I accomplishin preferred embodiments of my invention through the use of electricdischarge devices or tubes of the so-called screen grid pentode typeknown commercially as RCA-57, RCA-58 and the like.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organizalni and its method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of a speciflc embodiment, whenread in connection with the accompanying drawing, in which:

Figure 1 is a schematic circuit diagramof a direct connected electricdischarge amplifier for direct current and audio frequency signals downto relatively low frequency values, althouglhigher frequency signalssuch as radio frequency slg nals may be amplified thereby;

Fig. 2 is a similar` schematic circuit diagram of a relay circuitembodying two direct connected electric discharge devices arranged fortrigger" control;

Fig. 3ds/also a similar diagram of a. trigger relay provided with meanswhereby it is self restoring; and

Figs. 4, 5, and 6 are schematic circuit diagrams exemplifying theapplication of the invention to oscillators of the multi-vibrator type.

Referring to Fig. 1 of the drawing, which is fundamental to theremaining figures, an amplifier constructed according to my inventionpreferably comprises a plurality of electric discharge devices or tubesi and 3 of the so-called screengrid pentode type. The first tube I lsprovided with an anode 5, a suppressor grid 1, a screen grid 9, acontrol grid Il, and a cathode 55 I3. The second tube 3 is identical inconstruction and is also provided with an anode I5, a. suppressor grid|1, a screen grid I9, a control grid 2|, and a cathode 23.

The anodes of the severalltubes are connected to the positive terminalof `a plate potential source over resistors and 21 respectively, thelast-named resistor providing the output impedance of the system andbeing provided with output terminals E2. The green grid of the rst tube,I, is also connected to the positive lead of the plate potential sourceand a direct connection 26 extends from the plate of that tube to thescreen grid of the second tube, 3.

The cathodes of the several tubes are connectc together and to' thenegative terminal of the plate potential source. The control grid of therst tube is connected to the cathode through a grid leak I2 and isprovided'with input terminals E1 across said resistor. The control grid2| of the second tube. may be connected to its cathode directly orthrough a grid leak 22, as shown in the drawing.v

It will be noted from an inspection of Figure l of the drawing thatthere is no cross-connection from the plate of the second tube back tothe screen -grid of the rst tube. Such being the case, the-operatingcondition of the first tube is not appreciably influenced by thecondition of the second tube, and the system may be utilized as a directcurrent amplifier, or an amplifier for alternating current at anyfrequency from zero up to a limiting frequency determined by the inputcapacity of the tube.

The' operation of the system shown in Fig. l is as follows:

Direct current potentials or alternating current signal potentialsapplied to the input terminals designated at E1 are applied to thescreen grid I9 of the second amplifier stage through the couplingimpedance 25 in circuit with the anode 5 of the first amplifier stage.

Signals applied to the screen grid i9 are amplied and may be derivedfrom the anode circuit connected with the anode i5 and, in the presentexample, are taken in parallel with the output impedance 21 from theterminals E2.

This system has the advantage that since the screen grid I 9 and theanode 5 may operate at the same potentials they may be directlyconnected as shown, whereby the coupling system is reduced to a. singleimpedance device 25 and the usual coupling condenser is eliminated,thereby improving the frequency response. Furthermore, the usual highvoltage source of anode potentials or the separate battery source ofanode potentials and separate filament supply circuits ordinarilyyrequired by the usual D. C. amplier are not .required in the presentamplifier' system.

In the case that an additional stage of amplification is desired, asecond amplifier may be connected with the device 3 through the outputterminals E2 in the same manner as the device 3 is coupled to the deviceI, through a coupling imped-ance or resistor in the anode circuit of onedevice and a direct connection from the anode end thereof to the screengrid ofthe amplifier device in the succeeding amplifier stage.

Referring now to Fig. 2, a pair of electric discharge amplifier devices30 and 3| of the screen grid pentode type are shown connected in abalanced amplifier circuit similar to that of a multivibrator. In thiscircuit, however, the devices 30 and '3L do not operate as oscillatorsbut as relays of the trigger type. In this type of re' lay, a change incontrol grid voltage sets\the relay in action to cause a change in anodecurrent from one predetermined value to another.

In the present example, the anode 32 of the device 30 is provided with acoupling impedance 33 by which it is coupled through a connection' 34with the screen grid 35 of the second device 3|.. In a similar mannerthe anode 36 of the device 3| is coupled back through the impedance 31and connection 38 with the screen grid 39 of the first device 30. Theanodes and screen grids of the pair of amplifiers are thus crossconnected. Grid leak connections to the cathode are provided for thecontrol grids 40 through grid leak resistors 42 and 43. Likewise, thesuppressor grids 4I are connected to the cathodes whereby the sameoperating potentials may advantageously bev used on both anodes andscreen grids, thereby permitting a direct connection between amplifiersand common coupling imped- 20 The latter terminals are short-circuitedbut may be open-circuited for applying signal potentials to the grid 40.

The output circuits of the devices 30 and 3| may be connected to anysuitable utilization means and in the present example, the. outputcircuit for the device 3| is connected with a current responsive devicesuch as a relay 46 which is connected in series with the couplingimpedance 31 adjacent to the anode 36. A series output circuit isthereby provided for the device 3|.

However, itis desirable under certain circumstances, to utilize a shuntoutput connection, whichvis shown in connection withthe device 30, anoutput circuit therefor being indicated by the leads 4'|. It will benoted that these leads are connected between the anode and the cathodeof the device 30 and that the arrangement is such that the couplingdevice 33 is utilized as an output impedance for the leads 41.

The operation of the relay is as follows:

A small negative signal potential on the input terminals 44 causes areduction in the anode current of the first amplifier device 30 throughthe coupling impedance 33. This causes a reduction in the I. R. dropthrough the impedance and a corresponding increase in the potential onthe anode 32 of the iirst amplifier device 30 and on the screen grid 35of the second amplifier device 3|. The increased screen grid potentialcauses an increase in the anode current of the device 3| and acorresponding increase in the I. R. drop through the coupling impedance31.

The latter action results in a reduction of the potential on theanode 36and on the screen grid 39 and this in turn further decreases the anodecurrent through the impedance 33. This action slightly negative to startthe operation of the relay from the condition above described.

To restore the relay to its normal condition or to reverse the operationabove described, a positive potential may be applied to the grid 40 atthe terminals 44 or, preferably, a slightly negative potential isapplied to they grid 40 of the device 3| whereupon the relay operates toreduce the anode current of the device 3| to substantially zero and torestore it to normal through the device 30.

For the purpose of triggering the relay in either direction to actuatethe current responsive device 46 in circuit therewith or to restore therelay system to a normal condition of operation, a source of negative orpositive potential 48 may be provided in connection with the grids 4|),and this potential may be applied selectively to either of said grids,that is. between grid and cathode of either tube, through a suitableselective switching means 49 and grid potential supply leads 50. From aninspection of the circuit, it will be seen that the switch 49 may beclosed in either one of two directions to apply a potential from thesource 38 through the leads 50 to a selected one of the grids 4D.

The controlling potential for the relay may be applied to the inputterminals 45 for the device 3| by removing the short circuit therefromand the signal output from the relay system may be taken from the outputimpedance 33 through the output leads 41.

'I'he use of a separate input circuit for each of the devices 3U and 3|has the advantage that the system may be utilized to respond to twodifferent control voltages if applied thereto in proper sequence.

'Ihe anode current in one of the devices 30 or 3| is alwayssubstantially zero and at a maximum in the other. A small negativepotential on the grid of the device taking anode current will cause theanode current to suddenly and completely drop to substantially zero andthe anode current of the other device to as suddenly and completelyincrease to a maximum. The relay is therefore of the trigger type, butis somewhat different from the usual type in that the change from zeroto maximum plate current has no intermediate stopping point and issubstantially instantaneous.

Relatively low positive potential on the other grid, that is the grid ofthe device not taking plate current will cause the same result. It hasbeen found that a control potential of less than 1.5 volts, withsuitable amplifier devices such as the RCA- 57 and RCA-58 tubes willprovide a Wide change of voltage in the plate resistors, which may be inthe order of a hundred or more volts.

By way of example, the coupling resistors or impedances 33 and 3'! mayhave a value of substantially twenty to thirty thousand ohms, while theinput coupling impedance or grid leak resistors 42 and 43 may have anydesired value, depending upon the impedance of the input circuit and thevoltages to be applied to the control grids. The anode potential supplyleads indicated at 5| and 52 may be supplied direct current potentialsof substantially 250 volts for tubes of the type hereinbeforedesignated.

With the circuit arrangement as above described, it will be seen thatthe application of a positive potential to the grid of the device inwhich the plate current is maximum will have no affect upon theequilibrium of the system, whereas the application of even a slightlynegative potential thereto will cause the relay to be actuated.

The application of vcontrolling or triggering potentials alternately tothe control grid circuits for actuating the relay circuit inalternatedirections must therefore occur in a predetermined sequence.

In this circuit also, advantage is taken of the 5 fact that the screengrids of screen grid pentode' devices may be connected withfthe samepotential source as the anodes, whereby the anodes and screen gridsofthe relay device may be interconnected directly without couplingcondensers or 10 the like as in the preceding amplifier circuit ofFig. 1. 'Ihe use of the suppressor grid permits plate voltage to be thesame as the screen voltage Without a loss of efficiency.

. Referring now to Fig. 3, /a trigger relay similar 15 to that shown inFig. 2 is further provided with means whereby it is automaticallyrestored to a normal operating condition upon completion of theoperating cycle. In this figure, the circuit connections and circuitelements are sub- 20 stantially the same as in Fig. 2 and bear the samereference numerals.

It will be noted that the amplifier device 3| is provided with signal orcontrol voltage input terminals, connected across the grid circuit re-25 sistor 43 of the device 3| for applying controlling potentials to thecontrol grid 4Il of said device. 'I'he device 3| is, therefore, thefirst amplifier in this circuit.

Having selected the device as a first amplifier 30 for receiving ,thecontrolling potentials, the second control grid, that is the controlgrid of the second amplifier device 3|! is coupled with the screen gridof the same device, through a coupling condenser. 'I'his condenser isshown at 53, connected between the screen grid 39 and the adjacentcontrol grid 40 of the device 30. The specific circuit arrangement issuch that the condenser 53 and the grid impedance 42 provide a timedelay filter or network in connection with the said second control grid,the first control grid being considered as that selected to receivecontrolling potentials directly as above indicated.

It will be noted that there is also provided in connection with each ofthe control grid circuits a source of biasing potential arranged toprovide a higher negative bias on one grid than upon the other. In thepresent example the device 3U is provided with a higher biasingpotential from a source, 55 than the corresponding biasing potentialobtained from a source 54, for the device 3|.

The operation of the system described is as follows:

A short signal impulse applied to the input terminals 56 is *applied tothe grid of the first amplifier device or tube 3| and causes the relaysystem to pass through a complete cycle, the length of which dependsupon the capacity and impedance vvalues in the time delay network 6053-42 provided in connection with the second amplifier device 30.

When a negative impulse is applied to the control grid 40 of the device3| from the signal input terminals 56, the plate current of said devicedecreases to zero while the plate current of the device 30 increases toa maximum substantially in the same manner as described in connectionwith Fig. 2. Following this operation, the plate current in the device3| increases and 70 the plate current in the device 30 decreases, theformer becoming maximum and the latter becoming substantially zerowhereupon the relay system is restored to normal and is ready for asecond control impulse.

The delay in the cycle results from the control effect of the delaynetwork comprising the cou- "lay circuit may operate to control a deviceconnected in circuit therewith such as the current responsive device 56.

If the time delay network is connected with the control grid having aless negative bias, then, instead of a relay which may be operated topass through a predetermined cycle in response to a signal controllingimpulse of any duration, an oscillatory circuit is provided, thefrequency of oscillation being determined by the impedance of the timedelay network.

Such a circuit is shown in Fig. 4i to which attention is now directed,and in which the same reference numerals are applied to like parts as inFig. 3.

In Fig. 4, the screen grid pentode tubes dil and 3l are directlyinterconnected through anode coupling impedances 33 and Tl and gridleads 36 and 38. A relatively higher negative bias is provided by thesource 55 for the control grid dll of the device 3@ than is provided bythe source 54 for the corresponding control grid of the device 3l.

Grid impedances 42 and 43 are provided in the control grid circuits, andthe impedance d3 is connected with a coupling condenser 53 to the screengrid lead 34 so that the filter network is provided in connection withthe control grid to which the lower negative bias is supplied.

Output terminals are provided as indicated at 53, 59, 60 and 6l. Theoutput terminals 5B are in series with the anode 36 of the device 3l,adjacent thereto, and between the anode and the coupling impedance 31.The short circuit across the terminals 58 is removed when taking theoutput therefrom, and one of the terminals 58 and the terminal 59 may beemployed for taking the output from the coupling impedance 3l in shunttherewith. If desired, the output energy from the oscillator may betaken from other points in the anode circuit such as from the cathodereturn lead through the terminals til, in short circuit being removedfor this purpose.

In a similar manner, energy may be taken from the oscillator device 30as indicated by the terminals 6I provided in the cathode return lead andcorresponding to the terminals 63.

It has been found that in operation, in an oscillator device having atime delay network and the lower negative bias source of potential, asin this case for example, the oscillations are substantially rectangularin shape or square topped, while the wave shape oi' the oscillations inthe other device is more generally saw-toothed in form. Therefore, inthis type of cross-connected oscillator, wherein the coupling is directand the control grids are biased at differing potentials, a time delaynetwork may be applied, which permits two diiering wave forms to beprovided in the generated oscillations.

It has been found that the time delay network may be provided in serieswith the screen grid circuit as shown in Fig. 5, t0 which attention isnow directed. The time delay network is provided in the screen grid lead38 in the form of a variable impedance or resistor 62 and a condenser 63connected in shunt therewith'. This time delay network is connectedbetween the coupling impedance 31 of one amplifier device at the anodeend thereof, and the screen grid 39 of the other amplifier device.

The control grids 40 are provided with series impedance elements 42 and43, and it will be noted that the device 30, with which the time delaynetwork is connected, is provided with a lower negative bias on thecontrol grid. In this case, the bias potential is that of the cathode,while the device 3l is provided with a source 54 oi low negativepotential for the control grid 40.

It has been found that the output from this type of oscillator is steadyand its operation is stable over long periods of operation. The outputis taken from the output of the anode circuits by any suitableconnection such as hereinbefore described and as indicated by the seriesanode circuit output terminals 58. The use of the suppressor grid in theoscillator and amplifier circuits, as hereinbefore shown and described,materially aids in causing the circuits to operate without setting upundesired oscillations.

It will be seen that in the circuit shown, the suppressor grids areconnected with the cathodes. Likewise, the control grids are alsoconnected with cathode through an impedance device to which signals orcontrol potentials may be applied. The signals or potentials are derivedeither from an external source or from the screen grid circuit. Thescreen grids are directly connected with the anodes of the balanced pairof ampliilers or oscillator devices for the reason the circuitconnections are simplied and the suppressor grids tend to maintain theamplier devices in stable operation. The control grids are unbalanced bythe initial biasing means therefore, in order that the balanced pair ofdevices may be arranged to operate as a relay or as an oscillator.

The external source of bias potential may be eliminated by utilizing thepotential drop in anode circuit impedance devices, such as cathoderesistors 64 and 65, as shown in Fig. 6. In this circuit, the controlgrid of each amplifier or` oscillator device is connected through leads66 and 6l with' the cathode end of the bias resistor for the otherdevice.

A time delay network is provided in connection with each of the controlgrids by means of a condenser 68 connected from each control grid to thecathode and a variable series impedance or resistor 69 in each of thecontrol grid leads 66 and 61.

With this arrangement, the varying control potentials, existing acrossthe impedances or cathode resistors 64 and 65, are applied to thecontrol grids through the impedances 69 under control of condensers 6B,so that the potential changes on the control grids are relatively slowand maybe adjusted by adjusting the value of the impedances 69. Theoperation is otherwise the same as that for the oscillators shown anddescribed in Figs. 4 and 5 and the same vreference numerals are appliedto the same parts. The voltage output from each oscillator device is thesame, both being rectangular type waves.

An oscillator as shown and described, has the advantage that vigorousoscillations are produced and the signal output is relatively strong.The circuit has the further advantage that cathode lead impedancesprovide the source of biasing potential for the oscillator.

The voltage or signal output may be taken from the anode circuit ofeither device, substantially in the same manner as described inconnection with the preceding circuits, as from the terminals 58 and 59.

I claim as my invention:

1. In a relay system, the combination of a pair of electric dischargedevices each comprisingan anode, a cathode, a suppressor grid adjacentto the anode and connected to the cathode, a control grid adjacent tothe cathode, and a screen grid between said suppressor and controlgrids, an anode coupling impedance in circuit with each of said anodes,means providing a connection between each control grid and the cathode,means providing a direct connection between the anode of one device andthe screen grid of the other device, a condenser coupling the screengrid of one device to its control grid, a resistor connecting saidcontrol grid with the cathode of said device, and means for applying amore negative biasing potential to one of said control grids than to theother.

2. A balanced electric discharge delay circuit, including a pair ofscreen grid electric discharge amplifier devices conductivelyinterconnected between the cathode of one device and the control grid ofthe other device and between the anode of each device and the screengrid of each other device, means for stabilizing said circuit includinga suppressor grid in each of said devices connected to its cathode,means for applying a differing biasing potential on the control grids ofsaid devices, and a time delay circuit network interconnecting thecathode and two of the grid electrodes including the suppressor grid ofone of said devices and the anode of the other device.

3. A relay circuit including two electric discharge devices of thepentode type, a common coupling voltage drop producing impedanceconnected in circuit with the screen grid of one device and the anode ofthe other device, said circuit connection with said impedance providinga direct conductive connection between the last named screen grid andanode, the suppressor grids of said devices being connected to theirrespective cathodes for stabilizing said circuit, means for applyingdiffering biasing potentials to the control grids of said devices, and atime delay circuit network interconnecting the cathode and two of thegrid electrodes of said other device and the anode of said one device.

4. An oscillator circuit comprising a pair of electric discharge devicesof the pentode type, each having a screen grid interconnected directlywith the anode of the other device, a filter net- Work connected betweenthe cathode and control grid of one tube and the cathode and controlgrid of the other tube, a connection between each suppressor grid andits cathode, a source of potential, and a potential drop producingimpedance element in circuit with each cathode through said source tosaid anodes.

5; A multi-vibrator oscillator comprising in combination a pair ofelectric discharge devices of the pentode type, means for applyingdiffering negative biasing potentials to the control grids of saiddevice, a potential drop producing impedance element, the screen grid ofone device and the anode of the other device being directly coupledthrough said impedance element, the anode of said one device providingan output connection for said oscillator, a time delay filter comprisinga condenser and a resistor connected between the anode of said onedevice and the control grid of said other device, the resistor being incircuit between the cathode and the control grid of said other device.

6. A trigger amplifier comprising in combination, a pair of electricdischarge devices of the pentode type each having a cathode, an anode, asuppressor grid adjacent to the anode and connected to the cathode, acontrol grid adjacent to the cathode and a screen grid interposedbetween said suppressor and control grids, means providing a directconnection between each screen grid and the anode of the other device,anode output coupling impedances connected one with each anode, meansincluding an impedance device providing a connection between the controlgrid and the cathode of eachdevice, means for applying a controllingpotential to one of said control grids, means for biasing said grid at alower negative potential than the control grid of the other device, anda lter network connected with the screen and control grids of said otherdevice and between the cathode thereof and the anode of said onedevice,said lter network including a variable impedance device.

7. In an electric relay system, the combination of a pair of electricdischarge devices of the pentode type, having the anode of one devicedirectly connected with the screen grid of the other device, and eachhaving a suppressor grid and control grid connection with the cathodethereof, means for applying differing negative biasing potentials on thecontrol grids of said devices, means for applying controlling potentialimpulses selectively to the control grids of said de-. vices, and a timedelay circuit network interconsaid devices and the anode of said otherdevice.

W'INFIELD R. KOCH.

